The correct answer regarding the impact of World War II on the US population is:
A. Economic opportunities for Black Americans improved.
During World War II, the demand for labor increased significantly due to wartime production needs, which provided new job opportunities for Black Americans who had historically faced discrimination and limited economic opportunities. Many moved to industrial jobs in northern cities as part of the Great Migration.
Option B is incorrect because many women entered the workforce in large numbers during the war to fill roles vacated by men who went to fight.
Option C is also incorrect; while racial tensions persisted, the war effort laid groundwork for civil rights advancements in the post-war period.
Option D is not accurate; while there were challenges regarding workers' rights, the war also led to increased unions and labor movements advocating for workers' rights and protections.